Mobile terminal, control apparatus, home agent and packet communications method

ABSTRACT

In a packet communications system, a control apparatus implements routing control of a received packet directed for the mobile terminal. The mobile terminal includes a plurality of network interface cards; a communication manager configured to select at least one network interface card among from the plurality of network interface cards, in accordance with information regarding the network interface card; and an upper layer manager configured to receive the packet transmitted from the control apparatus, with using a selected network interface card.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and is based upon and claims thebenefit of priority under 35 U.S.C. § 120 for U.S. Ser. No. 10/886,637,filed Jul. 9, 2004, and claims the benefit of priority under 35 U.S.C. §119 from Japanese Patent Application No. 2003-194484, filed Jul. 9,2003, the entire contents of each of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile terminal and a controlapparatus which are used in a packet communications system in which thecontrol apparatus implements routing control of a received packetdestined for the mobile terminal.

The present invention also relates to a mobile terminal and a controlapparatus which are used in a packet communications system implementingpaging control. In the paging control, the control apparatus transmits apaging notification packet to a paging area of the mobile terminal whenreceiving a packet destined for the mobile terminal, so as to acquirelocation information of the mobile terminal and to decide a transferdestination of the packet.

The present invention further relates to a mobile terminal and a homeagent which are used in a packet communications system in which aplurality of home agents implement routing control of a received packetdestined for the mobile terminal, in accordance with each home addressand each care-of address.

2. Description of the Related Art

A conventional packet communications system has been configured toconfirm reachability of an IP packet, by using the address resolutionprotocol (ARP) or the neighbor discovery protocol (NDP), prior to thetransfer of the IP packet using a unicast address.

The ARP and NDP are defined to associate a link layer address (or a cardaddress) of a network interface card and a network layer address (an IPaddress) with each other.

Note that an IP address is decided by means of static setting where theIP address is assigned to a network interface card in advance, or bymeans of dynamic setting such as the dynamic host configuration protocol(DHCP). Alternatively, an IP address is decided by calculation using anaddress automatic generation technology used in IPv6, based on a networkinterface card address on a link layer and random numbers.

In the conventional packet communications system, when a mobile terminal(a mobile node or a host) has a plurality of network interface cards asmeans for allowing a packet to reach its destination, acustomer-oriented interface application technology is implemented as aninteractive application technology such as an access link manager.

In this customer-oriented interface application technology, for example,a network interface card corresponding to a communication link systemhaving low communication costs is selected among from the plurality ofnetwork interface cards.

In such a case, a multiple interface manager (MIM), which manages aplurality of network interface cards, is known as a method of selectinga network interface card autonomously.

The MIM is configured to make a predetermined conditional decision usingattributes and measured values collected from each of the networkinterface cards, so as to select a network interface card to be used.

Conventionally, a packet communications system which implements amobility management control technology including a Mobile IP technologyand an expansion technology of the Mobile IP technology has been knownas a communications system which enables transfer of a packet destinedfor a mobile terminal.

In the mobility management control technology, a home address is used asa controlling unit of packet transfer.

Here, the home address is assigned to each mobile terminal on a homelink where a home agent exists, and, for example, the home address is anIP address which belongs to a subnet of the home link.

The packet communications system, which implements the abovementionedmobility management control technology, is configured to perform routingcontrol independently by using each home address as a unit, when amobile terminal (a mobile node) has a plurality of home addresses asmeans for allowing a packet to reach its destination, for example, whenthe mobile terminal is connected to a plurality of home agents dependingon application of the mobile terminal and a kind of communicationssystem being used, or when the mobile terminal is in a multi-homesituation where the mobile terminal has a plurality of home addresseswithin the same home agent.

However, in the technique of selecting a network interface card in theconventional packet communications system, an IP address (network layeraddress) is not particularly considered, and correspondence between thenetwork interface card and the IP address is thus not maintained.

Therefore, the conventional technique of selecting a network interfacecard has a problem in that address resolution means, such as the ARP andthe NDP, is required in order to acquire the abovementionedcorrespondence, every time a network interface card to be used changes,even among network interface cards to which the same IP address has beenassigned.

The conventional technique of selecting a network interface card alsohas a problem in that an IP address to be used changes when a networkinterface card to be used changes, so that a procedure for changing apacket's route is required.

For example, in the IPv6 automatic address generation technology using alink layer address, an IP address to be used changes every time anetwork interface card to be used changes, even where the mobileterminal belongs to the same network domain, so that a procedure forchanging a packet's route is required.

Further, even in a case of automatic allocation (dynamic setting) of anIP address by the network side, like the DHCP, a procedure for changinga packet's route is required. This is because network domains generallydiffer from each other when the kind or owner of the relevantcommunication link (access link) system is different. Therefore, a IPaddress to be used changes every time a network interface card to beused changes.

In other words, in the conventional packet communications system, amobile terminal is required to register an IP address with a controlapparatus (such as a routing control agent and a relay agent) within theIP network and with a transmitting terminal, every time a networkinterface card to be used changes. A packet is reached to the mobileterminal by using the IP address.

Therefore, the conventional packet communications system has a problemin that IP packets related to the aforesaid registration pass throughwireless links, so that wireless resources are wasted.

It is highly likely that this problem causes another problem in a pagingcontrol technology.

The paging control technology reduces an amount of control signalsrelated to location registration control of the mobile terminal, byregistering the location of the mobile terminal per paging area widerthan a location registration area, and also reduces power requirementstogether with an intermittent reception technology of the mobileterminal.

The problem in the paging control technology is that a paging agentcannot acquire location information (subnet) of the mobile terminalaccurately.

Meanwhile, the conventional mobility management technology does notmaintain the correspondence among a plurality of IP addresses assignedto the same mobile terminal.

Therefore, when an IP packet destined for the mobile terminal istransmitted and the IP packet cannot reach the mobile terminal through atransfer route generated based on a specific home address due to linkdisconnection or the like, the transfer of the IP packet fails evenwhere a transfer route generated based on a different home address isavailable and the IP packet could reach the mobile terminal through thetransfer route.

Further, the conventional packet communications system does not maintainthe correspondence among a plurality of IP addresses, even when themobile terminal dynamically changes validity and invalidity of theplurality of IP addresses in accordance with applications, communicationcosts, and power-saving control of network interface cards.

Therefore, the conventional packet communications system has a problemin that a transfer of a packet from a transmitting terminal to a mobileterminal fails.

In such a case, the mobile terminal notifies the transmitting terminalor a name resolution (DNS: domain name system) server of the changebetween validity and invalidity of the IP addresses by using a controlpacket, every time the mobile terminal changes validity and invalidityof the IP addresses.

Therefore, the conventional packet communications system has a problemin that resources are wasted according to the frequency of suchnotification.

SUMMARY OF THE INVENTION

In viewing of the foregoing, it is an object of the present invention toprovide a mobile terminal, a control apparatus, and a home agent, whichare used in a packet communications system capable of ensuringreachability of a packet without wasting wireless resources, even when anetwork interface card to be used changes.

A first aspect of the present invention is summarized as a mobileterminal in a packet communications system in which a control apparatusimplements routing control of a received packet directed for the mobileterminal. The mobile terminal includes a plurality of network interfacecards; a communication manager configured to select at least one networkinterface card among from the plurality of network interface cards, inaccordance with information regarding the network interface card; and anupper layer manager configured to receive the packet transmitted fromthe control apparatus, with using a selected network interface card.

In the first aspect, the packet communications system can be configuredto implement paging control in which the control apparatus transmits apaging notification packet to a paging area of the mobile terminal whenreceiving of the packet directed for the mobile terminal, so as toacquire location information of the mobile terminal and to decide atransfer destination of the packet. The communication manager caninclude a collector configured to collect link layer addresses set forthe network interface cards; and a decider configured to decide arepresentative link layer address among from collected link layeraddresses. The upper layer manager can include a notifier configured tonotify the control apparatus of the representative link layer address byusing the selected network interface card, when transmitting a pagingregistration packet for forming the paging area; and an address resolverconfigured to perform address resolution by using the representativelink layer address and a predetermined network layer address.

In the first aspect, the communication manager can further include arepresentative link layer address setter configured to set therepresentative link layer address to all the network interface cards.

In the first aspect, the communication manager can further include afiltering controller configured to instruct all the network interfacecards to stop an address filtering function on a link layer.

In the first aspect, the communication manager can further include acollector configured to collect link layer addresses set for the networkinterface cards. The upper layer manager can further include a notifierconfigured to notify the control apparatus of a predetermined networklayer address and collected link layer addresses, by using the selectednetwork interface card.

In the first aspect, the packet communications system can be configuredto implement paging control in which the control apparatus transmits apaging notification packet to a paging area of the mobile terminal whenreceiving of the packet directed for the mobile terminal, so as toacquire location information of the mobile terminal and to decide atransfer destination of the packet. The notifier can be configured tonotify the control apparatus of the plurality of link layer addressestogether with a paging registration packet for forming the paging area.

In the first aspect, each of a plurality of home agents can beconfigured to implement routing control of a received packet destinedfor the mobile terminal, in accordance with each home address and eachcare-of address, in the packet communications system. Each of theplurality of network interface cards can be configured to be connectableto the plurality of home agents. The upper layer manager can include amanager configured to manage to associate each of the network interfacecards with each of the home addresses; and an instructor configured toinstruct the plurality of home agents to transfer the packet destinedfor the mobile terminal to a home address associated with the selectednetwork interface card.

In the first aspect, the instructor can be configured to gives theinstruction to the plurality of home agents, by binding update for therepresentative home address.

In the first aspect, the packet communications system can be configuredto transfer the packet destined for the mobile terminal to the homeagents through a DNS server. The instructor can be configured toinstruct the DNS server to transfer the packet destined for the mobileterminal to the representative home address.

A second aspect of the present invention is summarized as a controlapparatus in a packet communications system implementing paging controlin which the control apparatus transmits a paging notification packet toa paging area of a mobile terminal, when receiving a packet destined forthe mobile terminal, so as to acquire location information of the mobileterminal and to decide a transfer destination of the packet. The controlapparatus includes a receiver configured to receive a representativelink layer address together with a paging registration packet from themobile terminal including a plurality of network interface cards; amanager configured to manage the paging area of the mobile terminal, inaccordance with a network layer address assigned to the mobile terminaland the received representative link layer address. The paging area ofthe mobile terminal is formed in accordance with the paging registrationpacket. The representative link layer address is decided among from linklayer addresses set for the network interface cards.

A third aspect of the present invention is summarized as_a controlapparatus in a packet communications system in which the controlapparatus implements routing control of a received packet destined for amobile terminal. The control apparatus includes a receiver configured toreceive a plurality of link layer addresses from the mobile terminalincluding a plurality of network interface cards; and a managerconfigured to manage routing control information for implementing therouting control in accordance with a network layer address assigned tothe mobile terminal and the plurality of representative link layeraddresses. Each of the plurality of link layer addresses being set foreach of the network interface cards

In the third aspect, the packet communications system can be configuredto implement paging control in which the control apparatus transmits apaging notification packet to a paging area of a mobile terminal whenreceiving the packet destined for the mobile terminal, so as to acquirelocation information of the mobile terminal and to decide a transferdestination of the packet. The receiver can be configured to receive theplurality of link layer addresses together with a paging registrationpacket from the mobile terminal including the plurality of networkinterface cards. The paging area of the mobile terminal is formed inaccordance with the paging registration packet. Each of the plurality oflink layer addresses is set for each of the network interface cards. Themanager can be configured to manage the paging area of the mobileterminal in accordance with the network layer address and the pluralityof received representative link layer addresses.

A fourth aspect of the present invention is summarized as a home agentin a packet communications system in which a plurality of home agentsimplement routing control of a received packet destined for a mobileterminal, in accordance with each home address and each care-of address.The home agent includes a receiver configured to receive arepresentative home address from the mobile terminal including aplurality of network interface cards; and a packet transferor configuredto transfer the packet destined for the mobile terminal to therepresentative home address. The representative home address is decidedamong from the home addresses associated with the network interfacecards.

In the fourth aspect, the home agent can further include a routinginformation manager configured to manage routing information destinedfor the representative home address. The packet transferor can beconfigured to transfer the packet destined for the mobile terminal, inaccordance with the routing information destined for the representativehome address. The routing information manager can be configured toupdate the routing information destined for the representative homeaddress in accordance with binding update from the mobile terminal.

In the fourth aspect, the packet communications system can include acontrol apparatus which transmits a paging notification packet to apaging area of the mobile terminal when receiving the packet destinedfor the mobile terminal, so as to acquire location information of themobile terminal and to decide a transfer destination of the packet. Therouting information destined for the representative home address is setso that the packet destined for the mobile terminal is transferred tothe control apparatus.

A fifth aspect of the present invention is summarized as a packetcommunications method in which a control apparatus implements routingcontrol of a received packet directed for a mobile terminal. The methodincludes selecting at least one network interface card among from aplurality of network interface cards included in the mobile terminal, inaccordance with information regarding the network interface card; andreceiving the packet transmitted from the control apparatus, with usinga selected network interface card.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a block diagram of the entire packet communications systemaccording to first to third embodiments of the present invention.

FIG. 2 is a functional block diagram of a mobile node according to thefirst embodiment of the present invention.

FIG. 3 is a functional block diagram of a routing control agentaccording to the first embodiment of the present invention.

FIG. 4 is a sequence diagram showing an operation of the packetcommunications system according to the first embodiment of the presentinvention.

FIG. 5 is a sequence diagram showing the operation of the packetcommunications system according to the first embodiment of the presentinvention.

FIG. 6 is a functional block diagram of a mobile node according to thesecond embodiment of the present invention.

FIG. 7 is a sequence diagram showing an operation of the packetcommunications system according to the second embodiment of the presentinvention.

FIG. 8 is a sequence diagram showing the operation of the packetcommunications system according to the second embodiment of the presentinvention.

FIG. 9 is a functional block diagram of a mobile node according to thethird embodiment of the present invention.

FIG. 10 is a view showing an example of managed content in a paging areamanaging unit of a routing control agent according to the thirdembodiment of the present invention.

FIG. 11 is a sequence diagram showing an operation of the packetcommunications system according to the third embodiment of the presentinvention.

FIG. 12 is a sequence diagram showing the operation of the packetcommunications system according to the third embodiment of the presentinvention.

FIG. 13 is a block diagram of the entire packet communications systemaccording to fourth and fifth embodiments of the present invention.

FIG. 14 is a functional block diagram of a mobile node according to thefourth and fifth embodiments of the present invention.

FIG. 15 is a functional block diagram of a home agent according to thefourth and fifth embodiments of the present invention.

FIG. 16 is a sequence diagram showing an operation of the packetcommunications system according to the fourth embodiment of the presentinvention.

FIG. 17 is a sequence diagram showing an operation of the packetcommunications system according to the fifth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views.

<Configuration of Packet Communications System According to the FirstEmbodiment of the Present Invention>

The configuration of a packet communications system according to a firstembodiment of the present invention is described with reference to FIGS.1 to 3.

As shown in FIG. 1, the packet communications system according to thisembodiment includes routing control agents MA and PA, access routers AR1and AR2, communication link systems AP1, BS1 and BS2, and a mobile nodeMN#1.

The packet communications system according to this embodiment isconfigured to implement paging control in which the routing controlagent (control apparatus) PA transmits a paging notification packet to apaging area of the mobile node MN#1, when receiving a packet destinedfor the mobile node (mobile terminal) MN#1, so as to acquire locationinformation (subnet) of the mobile node MN#1 and to decide a transferdestination of the packet.

As shown in FIG. 2, the mobile node MN#1 includes a plurality of networkinterface cards NIC#1 to NIC#n, a communication manager MIM, acontrolling unit 15, and an upper layer manager 100.

A MAC address (a link layer address) is set for each of the plurality ofnetwork interface cards NIC#1 to NIC#n.

The network interface card NIC#1 can be connected to the communicationlink system AP1, and the network interface card NIC#2 can be connectedto the communication link systems BS1 and BS2.

The mobile node MN#1 can be connected to an IP network by using thenetwork interface cards NIC#1 to NIC#n through the communication linksystems and access routers AR.

The communication manager MIM includes a link layer address collectingunit 11, a network interface card information storing unit 12, a networkinterface card deciding unit 13, and a representative link layer addresssetting unit 14.

The link layer address collecting unit 11 configures a collecting unitwhich collects the MAC addresses set for the network interface cardsNIC#1 to NIC#n, respectively.

The link layer address collecting unit 11 may also be configured tocollect characteristics of the network interface cards NIC#1 to NIC#n,together with the abovementioned MAC addresses, from the individualnetwork interface cards NIC#1 to NIC#n.

The network interface card information storing unit 12 is configured tostore information regarding the network interface cards, such as the MACaddresses and the characteristics, which are collected from theindividual network interface cards NIC#1 to NIC#n.

Here, the characteristics mentioned above include the kinds of linksystems to which the network interface cards can be connected,communication costs, power measurements (consumption power, SIR, etc.),precedence reflecting user preferences (utilization for business use orthe like), and so forth.

The network interface card deciding unit 13 is configured to select atleast one network interface card among from a plurality of networkinterface cards NIC#1 to NIC#n, in accordance with the informationregarding to the network interface card (the characteristics).

The network interface card deciding unit 13 is configured to decide arepresentative MAC address among from the MAC addresses collected by thelink layer address collecting unit 11.

The network interface card deciding unit 13 may be configured to selectthe network interface card which conform to a predetermined condition,in accordance with an instruction by a user, so as to select the MACaddress set for the selected network interface card as therepresentative MAC address.

The network interface card deciding unit 13 may be configured to selectthe network interface card and the representative MAC address, inaccordance with information (for example, a predetermined flag) which isadded to a packet to be transmitted.

Note that the network interface card deciding unit 13 may also beconfigured to decide a MAC address randomly selected among from thecollected MAC addresses, as a representative MAC address.

The representative link layer address setting unit 14 is configured toset the representative MAC address to all the network interface cardsNIC#1 to NIC#n.

The controlling unit 15 is configured to control all the functions ofthe mobile node MN#1 which includes the communication manager MIM andthe upper layer manager 100.

Moreover, the controlling unit 15 is configured to cause the mobile nodeMN#1 to operate in accordance with an operation mode (a normal mode or apaging control mode).

While operating in the normal mode, the mobile node MN#1 is controlledby the controlling unit 15 so that the mobile node MN#1 performsmobility management operations based on the mobile IP technology or theexpanded technology of the Mobile IP technology.

On the other hand, while operating in the paging control mode, themobile node MN#1 is controlled by the controlling unit 15 to suspend themobility management operations and to transmit a paging registrationpacket for forming a paging area to the routing control agent PA.

The upper layer manager 100 is configured to perform control operationson layers upper than the link layer (for example, on a network layer).

For example, the upper layer manager 100 collaborates with the routingcontrol agent MA as required, so as to perform control operations on anIP layer, realizing transmission and reception of an IP packet.

To be more specific, the upper layer manager 100 is configured toreceive the IP packet transmitted from the routing control agent (thecontrol apparatus) PA, by using the network interface card selected bythe network interface card deicing unit 13 of the communication managerMIM.

Also, the upper layer manger 100 is configured to notify the routingcontrol agent (control apparatus) PA of the representative MAC address,when transmitting the paging registration packet for forming a pagingarea of the mobile node MN#1 to the routing control agent PA. Here, thepaging registration packet may contain an IP address and therepresentative MAC address.

Further, the upper layer manager 100 is configured to perform addressresolution by the use of the representative MAC address and apredetermined IP address (a predetermined network layer address).

To be more specific, the upper layer manager 100 is configured toperform an address resolution procedure in which a correspondencebetween the representative MAC address and the predetermined IP address(the predetermined network layer address) is registered in the upperlayer manager 100, the communication manager MIM, the network interfacecard to be used, communication link system AP1 and the access routerAR1.

As a result, the MAC address to be used does not change even when thenetwork interface card NIC to be used changes. Therefore, the mobilenode MN#1 can continue its communication without any address resolutionprocess such as the ARP, the NDP, and the like.

Further, similarly to the above, when the mobile node MN#1 exists in arouter segment where an IP address is assigned to the mobile node MN#1by automatic generation of the IP address based on the MAC address setfor the network interface card NIC, the MAC address to be used does notchange, so that the IP address does not change either.

Therefore, there is no route change when the network interface card NICto be used changes on communication links within the same routersegment.

Note that the mobile node MN#1 is not required to transmit the pagingregistration packet because the MAC address to be used and the IPaddress to be used do not change, even when the network interface cardto be used NIC changes.

Therefore, the number of transmitted paging registration packets can besuppressed.

As shown in FIG. 3, the routing control agent PA is a control apparatusincluding a paging registration packet receiving unit 31, a paging areaforming unit 32, a paging area managing unit 33, a packet detecting unit34, a paging notification packet transmitting unit 35, a pagingnotification acknowledgement packet receiving unit 36, and a packettransferring unit 37.

The paging registration packet receiving unit 31 is configured toreceive the paging registration packet for forming a paging area of themobile node MN#1, which has been transmitted from the mobile node MN#1,and then to transmit the paging registration packet to the paging areaforming unit 32.

Also, the paging registration packet receiving unit 31 is configured toreceive the representative MAC address together with the abovementionedpaging registration packet, from the mobile node MN#1 which includes theplurality of network interface cards NIC#1 to NIC#n.

The representative MAC address has been decided among from the MACaddresses set for the network interface cards NIC#1 to NIC#n,respectively.

Further, the paging registration packet receiving unit 31 transmits apaging registration response packet to the mobile node MN#1, through theaccess router AR1, the communication link system AP1, the networkinterface card NIC#1 and the communication manager MIM.

The paging registration response packet notifies the mobile node MN#1that the paging area has been formed.

The paging area forming unit 32 is configured to form the paging area ofthe mobile node MN#1 in accordance with the received paging registrationpacket.

For example, the paging area forming unit 32 forms subnets #1 and #2 asthe paging area of the mobile node MN#1 in accordance with informationindicating the subnets which is contained in the received pagingregistration packet.

The paging area managing unit 33 is configured to manage the paging areaof the mobile node MN#1.

For example the paging area managing unit 33 stores an “IP address”, a“MAC address” and a “paging area” while associating them with eachother.

In the example shown in FIG. 3, the paging area managing unit 33 manages“IP_MN#1” as the IP address, “representative MAC address #1” as the MACaddress, and “subnets #1 and #2” as the paging area.

In other words, the paging area managing unit 33 configures a managingunit which manages the paging area of the mobile node MN#1 based on theIP address “IP_MN#1” assigned to the mobile node MN#1 and the receivedrepresentative MAC address “representative MAC address #1”.

The packet detecting unit 34 is configured to detect and buffer an IPpacket destined for the mobile node MN#1, and to notify this fact to thepaging notification packet transmitting unit 35.

The packet detecting unit 34 is further configured to transmit thebuffered IP packet destined for the mobile node MN#1, in accordance withan instruction from the packet transferring unit 37.

The paging notification packet transmitting unit 35 is configured totransmit the paging notification packet to the subnets #1 and #2 whichform the paging area of the mobile node MN#1, in accordance with thenotification from the packet detecting unit 34.

The paging notification acknowledgement packet receiving unit 36 isconfigured to receive a paging notification acknowledgement packettransmitted from the mobile node MN#1, and to notify the packettransferring unit 37 of the receipt of the packet.

The packet transferring unit 37 is configured to extract an IP packetcorresponding to the received paging notification acknowledgementpacket, from the packet detecting unit 34.

The packet transferring unit 37 is configured to transfer the extractedIP packet, in accordance with the subnets of the mobile node MN#1, whichare contained in the paging notification acknowledgement packet.

The access routers AR1 and AR2 are located within the IP network, andeach of the access routers AR1 and AR2 is configured to perform arouting process based on the IP address.

For example, the access router AR1 is connected to the communicationlink systems AP1 and BS1, and manages the subnet #1. The access routerAR2 is connected to the communication link system BS2, and manages thesubnet #2.

The communication link systems are connected to the access routers ARs,and each of the communication link systems is configured to performtransfer control on the link layer based on the MAC addresses.

<Operation of Packet Communications System According to the FirstEmbodiment>

The operation of the packet communications system according to thisembodiment is described with reference to FIGS. 4 and 5.

As shown in FIG. 4, in Step 401, the mobile node MN#1 is powered up, orthe network interface card NIC is added to the mobile node MN#1.

In Step 402, the link layer address collecting unit 11 collects the MACaddresses set for the network interface cards NIC#1 to NIC#n,respectively.

In Step 403, the network interface card deciding unit 13 decides arepresentative MAC address among from the collected MAC addresses, andalso decides the network interface card NIC#1 to be used.

In Step 404, the representative link layer address setting unit 14 setsthe representative MAC address for all the network interface cards NIC#1to NIC#n.

In Step 405, the upper layer manager 100 performs an address resolutionprocess between the upper layer manager 100 and the access router AR1,through the communication manager MIM, the network interface card NIC#1,and the communication link system AP1, by using the abovementionedrepresentative MAC address and a predetermined IP address.

In other words, in Step 405, the correspondence between therepresentative MAC address and the predetermined IP address isregistered in the upper layer manager 100, the communication managerMIM, the network interface card NIC#1, the communication link systemAP1, and the access router AR1.

In Step 406, the controlling unit 15 starts an operation in the pagingcontrol mode.

In Steps 407 to 411, the upper layer manager 100 transmits a pagingregistration packet which contains the aforesaid representative MACaddress and the predetermined IP address, to the routing control agentPA, through the communication manager MIM, the network interface cardNIC#1, the communication link system AP1, and the access router AR1, bythe use of the aforesaid representative MAC address and the IP address,without carrying out a new address resolution process.

In other words, in Steps 407 to 411, the upper layer manager 100, thecommunication manager MIM, the network interface card NIC#1, thecommunication link system AP1, and the access router AR1 transfer thepaging registration packet, in accordance with the registeredcorrespondence, respectively.

In Step 412, the paging area forming unit 32 forms a paging area (forexample, the subnets #1 and #2) associated with the abovementionedrepresentative MAC address and the predetermined IP address, inaccordance with the received paging registration packet.

In Steps 413 to 417, the paging registration packet receiving unit 31transmits a paging registration response packet to the upper layermanager 100 of the mobile node MN#1, through the access router AR1, thecommunication link system AP1, the network interface card NIC#1, and thecommunication manager MIM, by using the abovementioned representativeMAC address and the IP address, without carrying out a new addressresolution process.

The paging registration response packet is a packet for notifying theupper layer manager 100 that the paging area has been formed.

In other words, in Steps 414 to 417, the access router AR1, thecommunication link system AP1, the network interface card NIC#1, thecommunication manager MIM, transfer the paging registration responsepacket, in accordance with registered the correspondence, respectively.

As shown in FIG. 5, in Step 501, the network interface card decidingunit 13 decides to change the network interface card to be used from thenetwork interface card NIC#1 to the network interface card NIC#2.

In Step 502, the controlling unit 15 instructs the network interfacecard NIC#2 to start its operation.

In Step 503, the network interface card NIC#2 establishes acommunication link between the network interface card NIC#2 and thecommunication link system BS1, by using the set representative MACaddress.

In Step 504, the network interface card NIC#2 notifies the controllingunit 15 that the network interface card NIC#2 has started its operation.

In Step 505, the controlling unit 15 instructs the network interfacecard NIC#1 to suspend its operation.

In Step 506, the network interface card NIC#1 releases the communicationlink between the network interface card NIC#1 and the communication linksystem AP1, by using the set representative MAC address.

In Step 507, the network interface card NIC#1 notifies the controllingunit 15 that the network interface card NIC#1 has suspended itsoperation.

In Step 508, the packet detecting unit 34 of the routing control agentPA receives a packet destined for the mobile node MN#1.

In Step 509, the paging notification packet transmitting unit 35transmits a paging notification packet to the access router AR1.

The paging notification packet is a packet for notify the access routerAR1 that the packet destined for the mobile node MN#1 has been received.

In Step 510, the access router AR1 transmits the abovementioned pagingnotification packet to the communication link systems AP1 and BS1 whichmanage the paging area of the mobile node MN#1, that is, the subnets #1and #2.

In Steps 511 and 512, the communication link systems AP1 and BS1transmit the abovementioned paging notification packet to the networkinterface cards NIC#1 and NIC#2, respectively, by using the foregoingrepresentative MAC address and the IP address, without carrying out anew address resolution process. Here, the paging notification packetmentioned above is not received by the network interface card NIC#1.

In other words, in Steps 511 and 512, the communication link systems AP1and BS1 transmit the paging notification packet to the network interfacecards NIC#1 and NIC#2, in accordance with the registered correspondence,respectively.

In Steps 513 and 514, the paging notification packet received by thenetwork interface card NIC#2 is transmitted to the upper layer manager100.

In Steps 515 to 519, the upper layer manager 100 transmits a pagingnotification acknowledgement packet corresponding to the abovementionedpaging notification packet, to the routing control agent PA, through thecommunication manager MIM, the network interface card NIC#2, thecommunication link system BS1, and the access router AR1, by using theforegoing representative MAC address and the IP address, withoutcarrying out a new address resolution process.

In other words, in Steps 515 to 519, the upper layer manager 100, thecommunication manager MIM, the network interface card NIC#2, thecommunication link system BS1, and the access router AR1 transfer thepaging notification acknowledgement packet, in accordance with theregistered correspondence, respectively.

In Step 520, the packet transferring unit 37 extracts the packetdestined for the mobile node MN#1, which has been buffered in the packetdetecting unit 34, in accordance with the received paging notificationacknowledgement packet.

In Steps 521 to 525, the packet transferring unit 37 transmits thepacket destined for the mobile node MN#1 to the upper layer manager 100,through the access router AR1, the communication link system BS1, thenetwork interface card NIC#2 and the communication manager MIM, by usingthe foregoing representative MAC address and the IP address, withoutcarrying out a new address resolution process.

In other words, in Steps 522 to 525, the access router AR1, thecommunication link system BS1, the network interface card NIC#2, thecommunication manager MIM, transfer the packet destined for the mobilenode MN#1, in accordance with the registered correspondence,respectively.

<Operational Effect of Packet Communications System According to theFirst Embodiment of the Invention>

According to the packet communications system of this embodiment, theaddress resolution is conducted by using the representative MAC address(the representative link layer address) and the predetermined IP address(the network layer address) even when the mobile node MN#1 includes theplurality of network interface cards NIC#1 to NIC#n. Therefore,generation of an IP packet (for example, a paging registration packet)accompanied by the change of the network interface card NIC to be usedcan be prevented.

Moreover, according to the packet communications system of thisembodiment, the representative MAC address is decided based onapplications, communication quality, communication costs, power-savingcontrol and the like. Therefore, all packets can be received throughoptimal transfer routes which satisfy various conditions.

<Packet Communications System According to the Second Embodiment of thePresent Invention>

A packet communications system according to a second embodiment of thepresent invention is described with reference to FIGS. 6 to 8.

Description below is mainly about differences of the packetcommunications system according to this embodiment from the packetcommunications system according to the foregoing first embodiment.

As shown in FIG. 6, the mobile node MN#1 according to this embodimentincludes a filtering controlling unit 16 and does not include the linklayer address collecting unit 11 and the representative link addresssetting unit 14. Otherwise, the configuration of the mobile node MN#1 ofthis embodiment is the same as that of the mobile node MN#1 of theforegoing first embodiment.

The filtering controlling unit 16 is configured to instruct all networkinterface cards NIC#1 to NIC#n to start and stop an address filteringfunction on a link layer.

The operation of the packet communications system according to thisembodiment is described with reference to FIGS. 7 to 8.

As shown in FIG. 7, in Step 701, a mobile node MN#1 is powered up, or anetwork interface card NIC is added to the mobile node MN#1.

In Step 702, the filtering controlling unit 16 instructs all the networkinterface cards NIC#1 to NIC#n to stop the address filtering function onthe link layer.

In Step 703, a network interface card deciding unit 13 decides arepresentative MAC address among from collected MAC addresses, and alsodecides the network interface card NIC#1 to be used.

In Step 704, a controlling unit 15 instructs the network interface cardNIC#1 to start its operation.

In Step 705, the network interface card NIC#1 establishes acommunication link between the network interface card NIC#1 and acommunication link system AP1, by the use of a MAC address #1 set forthe network interface card NIC#1.

In Step 706, the controlling unit 15 instructs the network interfacecards NIC#2 to NIC#n to suspend their operations.

In Step 707, an upper layer manager 100 carries out an addressresolution process between the upper layer manager 100 and an accessrouter AR1, through a communication manager MIM, the network interfacecard NIC#1, and the communication link system AP1, by the use of theaforementioned representative MAC address and a predetermined IPaddress.

In other words, in Step 707, the correspondence between therepresentative MAC address and the predetermined IP address isregistered in the upper layer manager 100, the communication managerMIM, the network interface card NIC#1, the communication link systemAP1, and the access router AR1.

In Step 708, the controlling unit 15 starts an operation in a pagingcontrol mode.

In Steps 709 to 713, the upper layer manager 100 transmits a pagingregistration packet containing the aforementioned representative MACaddress and the predetermined IP address, to a routing control agent PA,through the communication manager MIM, the network interface card NIC#1,the communication link system AP1 and the access router AR1, by usingthe abovementioned representative MAC address and the IP address,without carrying out a new address resolution process.

In other words, in Steps 709 to 713, the upper layer manager 100, thecommunication manager MIM, the network interface card NIC#1, thecommunication link system AP1, and the access router AR1 transfer thepaging registration packet, in accordance with the registeredcorrespondence, respectively.

In Step 714, a paging area forming unit 32 forms a paging area (forexample, subnets #1 and #2) associated with the abovementionedrepresentative MAC address and the predetermined IP address, inaccordance with the received paging registration packet.

In Steps 715 to 719, a paging registration packet receiving unit 31transmits a paging registration response packet to the upper layermanager 100 of the mobile node MN#1, through the access router AR1, thecommunication link system AP1, the network interface card NIC#1 and thecommunication manager MIM, by using the aforementioned representativeMAC address and the IP address, without carrying out a new addressresolution process.

The paging registration response packet is a packet for notifying theupper layer manager 100 that the paging area has been formed.

In other words, in Steps 716 to 719, the access router AR1, thecommunication link system AP1, the network interface card NIC#1, thecommunication manager MIM, transfer the paging registration responsepacket, in accordance with registered the correspondence, respectively.

The operation of the packet communications system according to thisembodiment, shown in FIG. 8, is the same as that of the packetcommunications system according to the first embodiment, shown in FIG.5.

In the packet communications system according to this embodiment, thenetwork interface card NIC transfers all the received packets to theupper layer manager 100 even when a MAC address (a representative MACaddress) given to each of those packets is different from the MACaddress set for each network interface card NIC. Therefore, a newaddress resolution process is not generated by the change of the networkinterface card NIC within the same subnet.

<Packet Communications System According to the Third Embodiment of thePresent Invention>

A packet communications system according to a third embodiment of thepresent invention is described with reference to FIGS. 9 to 12.

Description below is mainly about differences of the packetcommunications system according to this embodiment from the packetcommunications system according to the foregoing first embodiment.

As shown in FIG. 9, a mobile node MN#1 according to this embodiment doesnot include the representative link address setting unit 14. Otherwise,the configuration of the mobile node MN#1 according to this embodimentis the same as that of the mobile node MN#1 according to the foregoingfirst embodiment.

Moreover, the mobile node MN#1 according to this embodiment isconfigured to notify a routing control agent PA of a predetermined IPaddress and a plurality of MAC addresses #1 to #n which have beencollected by a link layer address collecting unit 11 and respectivelyset for all network interface cards NIC#1 to NIC#n.

Specifically, an upper layer manager 100 is configured to notify therouting control agent PA of the abovementioned plurality of MACaddresses #1 to #n together with a paging registration packet.

Further, as shown in FIG. 10, a paging area managing unit 33 of therouting control agent PA according to this embodiment is configured tomanage a paging area “subnets #1 and #2” (in other words, routingcontrol information for implementing routing control) based on the IPaddress “IP_MN#1” assigned to the mobile node MN#1 and the plurality ofrepresentative MAC addresses #1 to #n.

The operation of the packet communications system according to thisembodiment is described with reference to FIGS. 11 and 12.

As shown in FIG. 11, in Step 1101, the mobile node MN#1 is powered up,or a network interface card NIC is added to the mobile node MN#1.

In Step 1102, the link layer address collecting unit 11 collects the MACaddresses set for network interface cards NIC#1 to NIC#n, respectively.

In Step 1103, a network interface card deciding unit 13 decides thenetwork interface card NIC#1 to be used.

In Step 1104, a controlling unit 15 instructs the network interface cardNIC#1 to start its operation.

In Step 1105, the network interface card NIC#1 establishes acommunication link between the network interface card NIC#1 and acommunication link system AP1, by using the MAC address #1 set for thenetwork interface card NIC#1.

In step 1106, an upper layer manager 100 carries out an addressresolution process between the upper layer manager 100 and an accessrouter AR1, through a communication manager MIM, the network interfacecard NIC#1 and the communication link system AP1, by the use of theforegoing MAC address #1 and a predetermined IP address.

In other words, in Step 1106, the correspondence between the MAC address#1 and the predetermined IP address is registered in the upper layermanager 100, the communication manager MIM, the network interface cardNIC#1, the communication link system AP1, and the access router AR1.

In Step 1107, the controlling unit 15 starts an operation in a pagingcontrol mode.

In Steps 1108 to 1112, the upper layer manager 100 transmits a pagingregistration packet containing the foregoing plurality of MAC addresses#1 to #n and the predetermined IP address, to the routing control agentPA, through the communication manager MIM, the network interface cardNIC#1, the communication link system AP1, and the access router AR1, byusing the foregoing MAC address #1 and the IP address, without carryingout a new address resolution process.

In other words, in Steps 1108 to 1112, the upper layer manager 100, thecommunication manager MIM, the network interface card NIC#1, thecommunication link system AP1, and the access router AR1 transfer thepaging registration packet, in accordance with the registeredcorrespondence, respectively.

In Step 1113, a paging area forming unit 32 forms a paging area (forexample, subnets #1 and #2) associated with the abovementioned MACaddresses #1 to #n and the predetermined IP address, in accordance withthe received paging registration packet.

In Steps 1114 to 1118, a paging registration packet receiving unit 31transmits a paging registration response packet to the upper layermanager 100 of the mobile node MN#1, through the access router AR1, thecommunication link system AP1, the network interface card NIC#1, and thecommunication manager MIM, by using the foregoing MAC address #1 and theIP address, without carrying out a new address resolution process.

The paging registration response packet is a packet for notifying theupper layer manager 100 that the paging area has been formed.

In other words, in Steps 1115 to 1118, the access router AR1, thecommunication link system AP1, the network interface card NIC#1, thecommunication manager MIM, transfer the paging registration responsepacket, in accordance with registered the correspondence, respectively.

As shown in FIG. 12, in Step 1200, a packet detecting unit 34 of therouting control agent PA receives a packet destined for the mobile nodeMN#1.

In Steps 1201 and 1204, a paging notification packet transmitting unit35 transmits a paging notification packet containing the MAC address #1and a paging notification packet containing the MAC address #2, to theaccess router AR1.

In Steps 1202 and 1205, the access router AR1 transmits theabovementioned paging notification packets respectively to thecommunication link systems AP1 and BS1 which manage the paging area ofthe mobile node MN#1, that is, the subnets #1 and #2.

In Step 1203, the communication link system AP1 attempts to establish acommunication link between the communication link system AP1 and thenetwork interface card NIC#1 by using the MAC address #1, but fails.

Meanwhile, in Step 1206, the communication link system BS1 establishes acommunication link between the communication link system BS1 and thenetwork interface card NIC#2 by using the MAC address #2.

In Step 1207, the communication link system BS1 transmits the foregoingpaging notification packets to the network interface card NIC#2, byusing the MAC address #2 and the IP address without carrying out a newaddress resolution process.

In other hand, the communication link system BS1 transmits the pagingnotification packets to the network interface card NIC#2, in accordancewith the registered correspondence.

In Steps 1208 and 1209, the paging notification packets received by thenetwork interface card NIC#2 are transmitted to the upper layer manager100.

In Step 1210, an address resolution process is carried out between theupper layer manager 100 and the access router AR1, through thecommunication manager MIM, the network interface card NIC#2, and thecommunication link system BS1, by using the foregoing MAC address #2 andthe predetermined IP address.

In other words, in Step 1210, the correspondence between the MAC address#2 and the predetermined IP address is registered in the upper layermanager 100, the communication manager MIM, the network interface cardNIC#2, the communication link system BS1, and the access router AR1.

In Steps 1211 to 1215, the upper layer manager 100 transmits a pagingnotification acknowledgement packet corresponding to the aforementionedpaging notification packets, to the routing control agent PA, throughthe communication manager MIM, the network interface card NIC#2, thecommunication link system BS1, and the access router AR1, by using theforegoing MAC address #2 and the IP address, without carrying out a newaddress resolution process.

In other words, in Steps 1211 to 1215, the upper layer manager 100, thecommunication manager MIM, the network interface card NIC#2, thecommunication link system BS1, and the access router AR1 transfer thepaging notification acknowledgement packet, in accordance with theregistered correspondence, respectively.

In Step 1216, a packet transferring unit 37 extracts the packet destinedfor the mobile node MN#1, which has been buffered in the packetdetecting unit 34, in accordance with the received paging notificationacknowledgement packet.

In Steps 1217 to 1221, the packet transferring unit 37 transmits thepacket destined for the mobile node MN#1 to the upper layer manager 100,through the access router AR1, the communication link system BS1, thenetwork interface card NIC#2, and the communication manager MIM, byusing the foregoing MAC address #2 and the IP address, without carryingout a new address resolution process.

In other words, in Steps 1218 to 1221, the access router AR1, thecommunication link system BS1, the network interface card NIC#2, thecommunication manager MIM transfer the packet destined for the mobilenode MN#1, in accordance with the registered correspondence,respectively.

<Packet Communications System According to the Fourth Embodiment of thePresent Invention>

A packet communications system according to a fourth embodiment of thepresent invention is described with reference to FIGS. 13 to 16.

Description below is mainly about differences of the packetcommunications system of this embodiment from the packet communicationssystem of the foregoing first embodiment.

As shown in FIG. 13, the packet communications system according to thisembodiment includes a routing control agent PA, home agents HA1 and HA2,access routers AR1 to AR3, communication link systems AP1, BS1, APn, anda mobile node MN#1.

In the packet communications system according to this embodiment, theplurality of home agents HA1 and HA2 implement routing control of areceived packet destined for the mobile node MN#1, in accordance witheach home address and each care-of address. In this embodiment, themobile node MN#1 is in a multi-home situation.

Further, as shown in FIG. 14, the mobile node MN#1 according to thisembodiment does not include the link layer address collecting unit 11and the representative link layer address setting unit 14, and includesa home address managing unit 101 and a controlling unit 102 within theupper layer manager 100. Otherwise, the configuration of the mobile nodeMN#1 according to this embodiment is the same as that of the mobile nodeMN#1 according to the foregoing first embodiment.

The home address managing unit 101 is configured to manage a “homeaddress”, a “home agent”, a “care-of address”, and a “network interfacecard NIC” while associating them with each other.

The controlling unit 102 collaborates with a controlling unit 15 toinstruct the home agents HA1 and HA2 to transfer a packet destined forthe mobile node MN#1 to a representative home address associated with arepresentative network interface card which is decided so as to receivethe packet destined for the mobile node MN#1.

As shown in FIG. 15, the home agent HA2 includes a routing informationmanaging unit 51, a packet receiving unit 52, a packet transferring unit53, and an update information receiving unit 54.

The routing information managing unit 51 is configured to manage routinginformation destined for the aforementioned representative home addressby associating the “home address” and a “transfer address” with eachother.

The packet receiving unit 52 is configured to receive various packetsthrough a company A network.

The packet transferring unit 53 is configured to refer to the routinginformation managing unit 51, and to transfer the packet destined forthe mobile node MN#1 to the representative home address.

The update information receiving unit 54 is configured to receivebinding update information from the mobile node MN#1, and to update therouting information destined for the representative home address, whichis contained in the routing information managing unit 51.

The operation of the packet communications system according to thisembodiment is described with reference to FIG. 16.

In this embodiment, the mobile node MN#1 enables only a networkinterface card NIC#1 which corresponds to a communication link systemwith the lowest communication costs, a network interface card NIC#1 usedby a user for business use, or a network interface card NIC#1 whichmakes the highest contribution to power savings.

The mobile node MN#1 disables the rest of the network interface cardsNIC and brings link down or stops their operations.

In such a case, when the home agent HA2, which manages a home addressHoA2 of the mobile node MN#1, exists in an internet service provider(ISP) providing an internet connection service by using thecommunication link system BS1 corresponding to the disabled networkinterface card NIC#2 or an IP network connected with the communicationlink system BS1, no packet can reach the mobile node MN#1 through atransfer route with the home agent HA2 as a base point, even where themobile node MN#1 has the network interface card NIC#1 which canestablish an enabled transfer route.

In order to resolve such a problem, the packet communications systemaccording to this embodiment operates as follows.

In Step 1501, a network interface card deciding unit 13 decides thenetwork interface card NIC#1 to be used as a representative networkinterface card.

In Steps 1502 and 1503, the controlling unit 15 transmits notificationof change from the network interface card NIC#2 to the network interfacecard NIC#1, to the network interface cards NIC#1 and NIC#2.

In Step 1504, the network interface card NIC#1 acquires a care-ofaddress LCoA1 which belongs to a subnet #1 in the communication linksystem AP1, from an access router AR1.

In Steps 1505 and 1506, the network interface card NIC#1 sends bindingupdate of the home address HoA1 and the care-of address LCoA1 (HoA1 toLCoA1) to the home agent HA1, thereby securing a transfer route betweenthe network interface card NIC#1 and the home agent HA1.

To be more specific, in Step 1504, a correspondence between each MACaddress and the acquired care-of address LCoA1 is registered in theupper layer manager 100, the communication manager MIM, the networkinterface NIC#1, and the access router AR1.

Further, in Steps 1505 and 1506, the routing information indicating totransfer a packet destined for the home address HoA1 to the care-ofaddress LoA1 is registered in the communication manager MIM, the networkinterface NIC#1, the access router AR1, and the home agent HA1.

In Steps 1507 to 1509, the network interface card NIC#1 sends bindingupdate of the home address HoA2 and the home address (the representativehome address) HoA1 (HoA2 to HoA1) to the home agent HA2 whichcorresponds to a transfer route through which packets cannot go due tothe aforementioned change of the network interface card.

To be more specific, in Steps 1507 to 1509, the routing informationindicating to transfer a packet destined for the home address HoA2 tothe home address HoA1 is registered in the communication manager MIM,the network interface NIC#1, NIC#2, the access router AR1, AR2, and thehome agent HA1, HA2.

In Step 1510, the home agent HA2 receives a packet destined for themobile node MN#1. The packet designates the home address HoA2 as thedestination address thereof.

In Step 1511, the home agent HA2 refers to the routing informationmanaging unit 51, and transfers the packet destined for the mobile nodeMN#1 to the home agent HA1.

In Steps 1512 to 1515, the packet destined for the mobile node MN#1,which has been received by the home agent HA1, reaches an upper layermanager 100 through the transfer route between the network interfacecard NIC#1 and the home agent HA1.

In this embodiment, when there are no packets to be transmitted andreceived, the mobile node MN#1 may be configured to stop sending thebinding update accompanied by the change of the access router AR wherethe mobile node MN#1 is located, so that packets destined for the mobilenode MN#1 are transferred to a routing control agent PA.

In such a case, all the home agents HA are set to transfer packetsdestined for the mobile node MN#1 to the routing control agent PA, thepackets designating the home addresses HoA managed by the home agents HAthemselves as the destination addresses of the packets.

As a result, all the packets destined for the mobile node MN#1 aretransferred to the routing control agent PA through any home agents HA.Therefore, paging is definitely performed.

<Packet Communications System According to the Fifth Embodiment of thePresent Invention>

A packet communications system according to a fifth embodiment of thepresent invention is described with reference to FIG. 17.

Description below is mainly about differences of the packetcommunications system according to this embodiment from the packetcommunications system according to the foregoing fourth embodiment.

The configurations of a mobile node MN#1 and home agents HA of thisembodiment are the same as those of the mobile node MN#1 and the homeagents HA of the foregoing fourth embodiment.

The operation of the packet communications system according to thisembodiment is described with reference to FIG. 17.

In Step 1601, a network interface card deciding unit 13 decides anetwork interface card NIC#1 as a representative network interface card,in accordance with a communication status of the mobile node MN#1, andthe like.

In Steps 1602 and 1603, a controlling unit 15 transmits notification ofthe change from a network interface card NIC#n to the network interfacecard NIC#1, to the network interface cards NIC#n and NIC#2.

In Step 1604, the network interface card NIC#1 acquires a care-ofaddress LCoA1 which belongs to a subnet #1 in a communication linksystem AP1, from an access router AR1.

In Steps 1605 and 1606, the network interface card NIC#1 sends bindingupdate of a home address HoA1 and the care-of address LCoA1 (HoA1 toLCoA1), to a home agent HA1, thereby securing a transfer route betweenthe network interface card NIC#1 and the home agent HA1.

To be more specific, in Step 1604, a correspondence between each MACaddress and the acquired care-of address LCoA1 is registered in theupper layer manager 100, the communication manager MIM, the networkinterface NIC#1, and the access router AR1.

Further, in Steps 1605 and 1606, the routing information indicating totransfer a packet destined for the home address HoA1 to the care-ofaddress LoA1 is registered in the communication manager MIM, the networkinterface NIC#1, the access router AR1, and the home agent HA1.

In Step 1607, an upper layer manager 100 performs DNS registration sothat a DNS server is instructed to transfer packets destined for themobile node MN#1 to the home address (the representative home address)HoA1.

The upper layer manager 100 of the mobile node MN#1 performs theabovementioned DNS registration, every time the change of the homeagent, which is caused by the change of the network interface card, isdetected.

According to the packet communications system of this embodiment, acorrespondent node CN can detect an enabled transfer route among from aplurality of transfer routes to the mobile node MN#1, through DNS.

As described so far, according to the present invention, it is possibleto provide a mobile terminal, a control apparatus, and a home agentwhich are used in a packet communications system which can ensure packetreachability without wasting wireless resources, even when a networkinterface card NIC to be used changes.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A mobile terminal in a packet communications system in which acontrol apparatus implements routing control of a received packetdirected for the mobile terminal, the mobile terminal comprising: aplurality of network interface cards; a communication manager configuredto select at least one network interface card from the plurality ofnetwork interface cards, in accordance with information regarding thenetwork interface card; and an upper layer manager configured to receivethe packet transmitted from the control apparatus, with using a selectednetwork interface card, and wherein each of a plurality of home agentsis configured to implement routing control of a received packet destinedfor the mobile terminal, in accordance with each home address and eachcare-of address, in the packet communications system; each of theplurality of network interface cards is configured to be connectable tothe plurality of home agents; and the upper layer manager comprises: amanager configured to manage to associate each of the network interfacecards with each of the home addresses; and an instructor configured toinstruct the plurality of home agents to transfer the packet destinedfor the mobile terminal to a home address associated with the selectednetwork interface card.
 2. The mobile terminal according to claim 1,wherein the instructor is configured to gives the instruction to theplurality of home agents, by binding update for the representative homeaddress.
 3. The mobile terminal according to claim 1, wherein the packetcommunications system is configured to transfer the packet destined forthe mobile terminal to the home agents through a DNS server, and theinstructor is configured to instruct the DNS server to transfer thepacket destined for the mobile terminal to the representative homeaddress.
 4. A home agent in a packet communications system in which aplurality of home agents implement routing control of a received packetdestined for a mobile terminal, in accordance with each home address andeach care-of address, the home agent comprising: a receiver configuredto receive a representative home address from the mobile terminalincluding a plurality of network interface cards, the representativehome address being decided among from the home addresses associated withthe network interface cards; and a packet transferor configured totransfer the packet destined for the mobile terminal to therepresentative home address.
 5. The home agent according to claim 4,further comprising a routing information manager configured to managerouting information destined for the representative home address; andwherein the packet transferor is configured to transfer the packetdestined for the mobile terminal, in accordance with the routinginformation destined for the representative home address, and therouting information manager is configured to update the routinginformation destined for the representative home address in accordancewith binding update from the mobile terminal.
 6. The home agentsaccording to claim 4, wherein the packet communications system comprisesa control apparatus which transmits a paging notification packet to apaging area of the mobile terminal when receiving the packet destinedfor the mobile terminal, so as to acquire location information of themobile terminal and to decide a transfer destination of the packet, andthe routing information destined for the representative home address isset so that the packet destined for the mobile terminal is transferredto the control apparatus.
 7. A packet communication method in which acontrol apparatus implements routing control of a received packetdirected for a mobile terminal, the method comprising: selecting atleast one network interface card from a plurality of network interfacecards included in the mobile terminal, in accordance with informationregarding the network interface card; receiving the packet transmittedfrom the control apparatus, with using a selected network interfacecard; implementing, at each of a plurality of home agents, routingcontrol of a received packet destined for the mobile terminal, inaccordance with each home address and each care-of address, theplurality of home agents connected by each of the plurality of networkinterface cards; associating each of the network interface cards witheach of the home addresses; and instructing the plurality of home agentsto transfer the packet destined for the mobile terminal to a homeaddress associated with the selected network interface card.